1. Field of the Invention
The present invention relates generally to a semiconductor device and a method for fabricating the same, and more particularly, to a semiconductor device capable of preventing contact defect and overcoming a limit in a process margin by employing a damascene process and a saddle fin transistor structure, and a method for fabricating the same.
2. Brief Description of Related Technology
Recently, as a design rule of a semiconductor device is sharply reduced to sub-40 nm technology, an area of an active region in which the device can be formed is also reduced. Accordingly, various limitations in a process margin are present. Particularly, abnormal shape of a gate line, i.e., leaning of the gate line or roughness of the gate line, is a serious problem. Also, in a landing plug contact process, contact defects are present in a great level due to the influence of the abnormal shape of the gate line and limitation in space.
With employment of a recently developed saddle fin transistor, an off-current margin property of a cell transistor is improved and thus the limitation in device properties can be overcome to some level. The saddle fin transistor can ensure a stable refresh property in a recess gate structure and, at the same time, enhance a cell driving current property by forming a bottom face of the recess gate in a fin transistor structure to enlarge a channel width. In the saddle fin transistor, an isolation layer formed in the semiconductor substrate is etched to protrude an active region, so that both side faces and an upper face of the active region are exposed. A gate is then formed so as to cover the exposed portion of the active region. Consequently, a channel is formed in the exposed three faces of the active region, and the driving current property through the channel thus can be enhanced.
However, patterning for a linear type recess structure and increase in the leaning of the gate line and the roughness of the gate line cause an increase in the contact defect in a self aligned contact (SAC) process. Also, due to reduction in an area to be formed with a device together with such contact defect, it is actually impossible to ensure a margin of SAC process. Therefore, a novel process capable of overcoming the contact defect and the limitation in the process margin is necessary.